1. Field of the Invention
The present invention is generally related to a direct fuel injection (DFI) system and, more particularly, to a direct fuel injection system that incorporates a common air rail with an air passage formed in the head of the engine, a common fuel rail with a fuel passage formed in the head of the engine, and a means for metering fuel into cylinders of the engine as a function of the pressure within the common fuel rail and the time that a fuel injection valve is opened.
2. Description of the Prior Art
Many types of direct fuel injection systems are known to those skilled in the art.
U.S. Pat. No. 5,694,905, which issued to Nuti on Dec. 9, 1997, discloses a fuel metering arrangement in pneumatically assisted direct fuel injection devices. The arrangement is used for pneumatically assisted direct fuel injection into an internal combustion engine cylinder head provided with a chamber housing a connecting rod for operating a compression piston slidingly guided within a jacket provided with one or more transfer conduits. The conduits connect the internal chamber to a variable dimension space positioned downstream of the piston and upstream of a valve providing access to a combustion chamber. Fuel feed means are connected to the variable dimension space. In this manner, a very rapid transient is achieved during acceleration.
U.S. Pat. No. 5,095,881, which issued to Nishimura et al on Mar. 17, 1992, describes a cylinder injection type internal combustion engine. A fuel air injection system for a two cycle crankcase compression internal combustion engine is described. A pressure accumulator is provided in the injector and the accumulator is charged with a compressed charge from the combustion chamber into which the injector injects during a phase of operation. In one embodiment of the invention, the accumulator chamber is charged during a compression stroke when ignition does not occur and in another embodiment of the invention, the accumulator chamber is charged during the same stroke of the engine when ignition occurs.
U.S. Pat. No. 5,666,927, which issued to Pace et al on Sep. 16, 1997, discloses a fuel/air supply system for a fuel injector and methods of operation. The fuel and air supply system provides fuel from a fuel pump at a first pressure upstream of a pressure reducer, with fuel being provided directly to the fuel injector at a reduced pressure on the downstream side of the pressure reducer. A bypass line is connected in communication with the fuel line upstream of the pressure reducer and provides fuel to an air reservoir at the first pressure. The air reservoir lies in communication with a porous member in the fuel injector in an air inlet to a fuel volume within the injector upstream of the pressure reducer.
U.S. Pat. No. 5,526,796, which issued to Thring et al on Jun. 18, 1996, discloses an air assisted fuel injector with timed air pulsing. A fuel injector valve controls both the metered flow of fuel and the metered flow of air into a mixing chamber, permitting intermittent, cyclic flow of both air and fuel into the chamber. The controlled cycling of both the air and fuel flow permits optimization of fuel performance. A single action valve and a dual action valve are disclosed. The air flow and fuel flow may be independently adjusted for maximum flexibility.
U.S. Pat. No. 5,390,647, which issued to Schechter on Feb. 21, 1995, describes an air charging valve for an air forced fuel injector. The valve is used with an air forced fuel injection system. The charging valve admits and stores compressed air from the engine cylinder and releases into the fuel injector to force out the air/fuel mixture into the engine cylinder. The charging valve accepts the pressurized air from the engine cylinder without allowing any air to escape back into the combustion chamber once it is in the air charging valve. The fuel injection system includes an injector having a fuel and air mixing chamber that includes a normally closed injector valve; the chamber being for premixing air and fuel before introduction of the compressed air which causes the fuel injection event.
U.S. Pat. No. 5,249,557, which issued to Katoh et al on Oct. 5, 1993, discloses a fuel injection system for a two cycle engine. The system is used for engines that employ a fuel injector that sprays into a chamber to which the compressed air is delivered and which chamber communicates with the combustion chamber through a port that is opened and closed by the reciprocation of the piston if applied to a reciprocating engine. The source of compressed air may either be an air compressor or a crankcase chamber of the engine and the air compressor and/or crankcase chamber may also provide scavenging air for the engine. A variety of port arrangements are disclosed which include either single ports or a plurality of ports either circumferentially or axially spaced from each other and disposed between either the scavenge ports and exhaust ports or around a scavenge or an exhaust port.
U.S. Pat. No. 5,170,766, which issued to Haas et al on Dec. 15, 1992, describes a fuel and air injection for a multi-cylinder internal combustion engine. The fuel and air assembly is provided for furnishing an air and fuel mixture under pressure to a cylinder of an ignition fired internal combustion engine which utilizes a solenoid-actuated valve timed to admit the mixture into the cylinder. A standard fuel injector is interfaced with one end of a mixing insert which is connected at the other end to an air passage of a fuel rail. At one side of the insert is an outlet passage leading to the solenoid actuated valve which has an outlet end shaped to enhance fuel distribution and combustion. The mixing insert contains an air filter and passages to conduct air to the common passage for air and fuel. The insert is captured in the fuel rail between a locating shoulder and the fuel injector for proper positioning relative to the timed valve. An adapter cap on the solenoid assembly joins the insert to the valve controlled passage to the cylinder.
U.S. Pat. No. 4,934,329, which issued to Lear et al on Jun. 19, 1990, describes a fuel injection system for a multi-cylinder engine. The system includes a rigid elongated unitary member incorporating a gas supply duct, a fuel supply duct, and a fuel return duct. Each of these extends in the direction of elongation of the unitary member. A separate fuel metering device and fuel injecting device is provided for each engine cylinder. The fuel metering device is arranged to deliver metered quantities of fuel to the fuel injection device and is in communication with the fuel supply and fuel return ducts so that fuel can be circulated through each of the fuel metering devices. The fuel injecting devices are each in communication with the gas duct and communicable with one of the engine cylinders. The fuel injection devices are adapted to effect delivery of a metered quantity of fuel entrained in gas supplied from the gas duct when the fuel injecting device is in fluid communication with a cylinder.
U.S. Pat. No. 4,899,714, which issued to Schechter et al on Feb. 13, 1990, discloses air/gas forced fuel injection system. A fuel injection system includes an injector having a fuel and air/gas mixing chamber that includes a normally closed injector valve, the injector being for premixing fuel and air. Controls provide a time interval between introduction of the fuel into the air chamber and the introduction of compressed air/gas to cause the injection event by opening of the valve to permit evaporation of the fuel whereby a premixed rich air/fuel mixture charge is discharged into the engine combustion chamber.
U.S. Pat. No. 4,693,224, which issued to McKay on Sep. 15, 1987, discloses a fuel injection method and apparatus. Gas is supplied to a fuel holding chamber to maintain a reference pressure which is above atmospheric pressure in the fuel holding chamber. A metered quantity of fuel is delivered into the holding chamber against the reference pressure. Communication is established between the holding chamber and the engine, and the supply of gas to the holding chamber is maintained while the communication exists so the pressure of the gas is sufficient to display the metered quantity of fuel from the holding chamber to the engine.
U.S. Pat. No. 4,759,335, which issued to Ragg et al on Jul. 26, 1988, describes a direct fuel injection by compressed gas. The fuel injection method and apparatus for in-cylinder injection in an internal combustion engine is disclosed. Compressed is used to inject the fuel through an injection nozzle particularly shaped so that different fuel spray patterns are produced at high and low fueling rates. At higher rates of fueling corresponding to higher engine loads the fuel spray pattern is narrowed and penetrates further into the cylinder volume whereas at lower rates of fueling corresponding to lower engine loads the fuel spray pattern is wider. The spray pattern is also less penetrating and relatively more confined. By appropriate selection of nozzle shape, the spatial distribution of the fuel spray droplets can be made to vary favorable over a range of engine loads.
U.S. Pat. No. 4,841,942, which issued to McKay on Jun. 27, 1989, discloses a method and apparatus for metering fuel. A continuous supply of fuel is provided by a pump to a fixed capacity chamber and gas under pressure is admitted periodically to the chamber to maintain in the chamber a pressure not greater than the fuel pressure so that fuel will flow into the chamber as long as there is a pressure differential between the gas in the chamber and the fuel supply. A delivery port in the chamber is opened for substantially the duration of the period that gas is admitted to the chamber so that the fuel in the chamber at the time of admission of gas thereto and fuel entering the chamber during the period of admission of gas, is delivered from the delivery port to the engine. The pressure differential between the fuel supply and the gas in the chamber is controlled in accordance with the fuel demand of the engine to control the quantity of fuel delivered each cycle to the engine. A preferred form of each of a fuel referencing regulator, a fuel regulator, and a metering and injection unit are described.
U.S. Pat. No. 5,069,189, which issued to Saito on Dec. 3, 1991, describes a fuel injection system for an internal combustion engine. Two embodiments of fuel/air injectors for an internal combustion engine are described wherein the main air delivery valve is actuated by a solenoid having a winding and wherein the solenoid winding is cooled by fuel in a jacket surrounding it which fuel is also delivered to the fuel injector. In one embodiment, the fuel injector solenoid and air control valve are all coaxial and in the other embodiment the fuel injector injects perpendicularly to the delivery valve and the solenoid.
U.S. Pat. No. 5,115,786, which issued to Yamada on May 26, 1992, discloses a fuel injection control system. The system includes an arrangement for opening the injector valve after the engine has stopped so as to purge the injector of any accumulated fuel. The injection valve may be opened and closed through a number of repeated cycles which assist in the removal of carbon deposits or may be held open for a fixed time period. In addition, if the injector is of the air/fuel type, any compressed air in the chamber can be utilized to purge the fuel and also the opening of the injection valve will preclude the accumulation of air pressure in the system after the engine has been shut down.
U.S. Pat. No. 5,095,873, which issued to Motoyama et al on Mar. 17, 1992, describes a fuel injection system and a method for an engine. The fuel injection system and control method for a two cycle crankcase compression internal combustion engine is disclosed wherein air and fuel are directly injected into the combustion chamber of the engine and the idle speed is maintained constant by varying the timing of fuel injection. Fine tuning of the idle speed is further accomplished by changing the duration of fuel injection under certain conditions.
U.S. Pat. No. 5,036,824, which issued to Albertson et al on Aug. 6, 1991, describes a fuel injection system. A fluid rail assembly supports a fuel metering injector and a charge delivery on an engine. The charge delivery injector includes flutes spaced about the interior of the nozzle to promote formation and delivery of a charge of fuel and air having desired spray characteristics. The fluid rail body includes passages that provide air to assist in delivering fuel from the fuel metering injector through the charged delivery injector to the engine, the passages being constructed to inhibit back flow of fuel therethrough.
U.S. Pat. No. 5,020,494, which issued to Plohberger et al on Jun. 4, 1991, discloses a method and device for feeding fuel into the combustion chamber of an internal combustion engine. Certain steps are followed to withdraw a small amount of compressed hot gas via a valve opening into the combustion chamber of the cylinder during one working cycle. This process also stores this small amount of hot gas, in a valve chamber of the valve, to inject fuel into the valve chamber containing the small amount of hot gas. It further builds a fuel/gas mixture and injects the fuel/gas mixture through the valve opening into the combustion chamber of the cylinder during the next working cycle of the internal combustion engine.
Existing direct fuel injection systems increase the cost of the engine significantly because of their complexity. In addition, because of the location of some of the known types of direct fuel injection systems relative to the head of the engine, the fuel/air mixture must travel a considerable distance to enter the cylinder. It would therefore be significantly beneficial if a direct fuel injection system could be provided which reduces the overall cost of the system and mixes the fuel and air within the structure of the engine head at a location which is close to the cylinder.